April 18, 2021

PCB Trace Width – Definition, Requirement, Importance, And Calculation

Today products like Smart TV, 4G, 5G Smartphones, Vehicle navigation systems, Automotive systems, Washing machines, Kitchen appliances, Aerospace, automotive, Space applications, drones need hardware as the requirement. A Printed Circuit Board (PCB) is the building block of the product hardware. PCB board design plays an important part. PCB trace width is important in board design.

What is PCB trace width?. Why so much importance?. PCB trace – The connection of any electric signal like digital, analog, power, a junction. The junction is a test point, empty pad, IC pin, or PCB plane. The width of the connection plays an important role in the circuit performance. PCB trace width measured in mils. PCB trace width is between 7 mils to 12 mils for simple circuits. As the PCB design complexity increases, the trace width requirement reduces. For military and space applications, the PCB trace width reduces to 2.5 mils and below. As PCB board design becomes complex as in multi-layered boards, the PCB trace width is an important factor to be considered.

PCB trace width needs optimization as per the PCB board design requirements. Board cost takes a back seat when circuit design requirements come into play. The circuit design has requirements like noise mitigation, speed optimization, Electromagnetic interference mitigation, noise coupling reduction, high voltage or current, temperature requirements from -33 degrees Celsius to 100 degrees Celsius. PCB trace width design is more important than cost reduction. The circuit performance depends on the PCB trace width design.

A PCB contains not one trace width but a variety of PCB trace widths. It depends, on the type of signal, connection, current, noise, ground plane. The bending of copper traces also affects the PCB trace width design. PCB with multiple trace widths depending on the requirement of the design and performance of the circuit. The board density and number of layers and stricter design requirements directly affect the trace width design. It is only performance, and cost has no factor or role in PCB trace width design.

PCB trace width calculated as per the IPC-2221standard. The standard is a set of data by which a PCB board design up to 35 amps of current, 400 mils of PCB trace width, temperatures between 10 degrees Celsius to 100 degrees Celsius, and 0.5 to 3 ounces per/sq feet of copper permitted. A majority of the tools in the market use the IPC-2221 data for PCB trace width design.

Designers often take the simple route of selecting the default PCB trace width in PCB board design. Not a good practice as it could lead to complications or malfunctions at a later stage. Always consider maximum current and reasonable temperature rise for power signals and impedance levels for signals. The copper layer, length of the track, the altitude of usage, and track curves also need to be considered.
PCB trace width design is crucial to PCB performance, and one needs to be an experienced person to design high-quality PCB boards. Always use the latest tools when deciding on the trace width.

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